1. Field of the Invention
This invention relates to air-powered tools, and more particularly to a hand-held turbine-driven orbital sander having a normally "off" double valve switch which reacts to pressure differential and biasing means to remain "on" after communicating the turbine with a source of vacuum.
2. Description of the Prior Art
Turbine driven vacuum cleaners have used various manually-operated gates and valves to regulate air flow through air chambers.
U.S. Pat. No. 1,323,925 shows a manually-adjusted gate at the end of a brush housing which changes the volume of air into the turbine cylinder.
U.S. Pat. No. 2,904,816 shows two independently operating valves, one of which is moveable to one of several positions to restrict airflow to the brush; it must be fixed in each position by a control knob. The other valve is spring-biased closed, but opens to reduce vacuum pressure between the nozzle and a rug.
U.S. Pat. No. 2,904,817 illustrates a single valve mounted between a turbine chamber and an outlet chamber. Again, it is held in various positions by a control knob.